I'm looking into Ikarus C42 specs - says empty weight - 265.5 KGs, MTOW - 450kg. so essentially it carries 184.5 kg payload, but that's not including fuel? what about the oil? Do I understand this correctly - if I have full tanks @ 65 liters, that's about 50 kilos, two passengers and their cargo should not exceed 135kg?

or looking at this another way around - two slim-bodied friends (how often does that happen, lol) want to take a ride, let's say with a total weight of 150kg (optimistic), you need a bottle of water, probably camera and some other gadgets, charts,snacks etc, adding another 10kg, they can only carry 25kg of fuel with them? that's not going to get you very far now is it? I guess my question is how do people tour in microlights if the limitations are so harsh? is microlight touring for solo flyers only?

Your numbers look correct and yes you have to be careful with Max AUW however many of the high performance microlights have ballistic recovery systems fitted with allows the MTOW be increased to 472.5Kg which (in the example) would give 47Kgs of fuel available which is about 60 litres. A lot of microlights only have 50 litre tanks fitted which will comfortably give you 4 hours endurance - at C42 speeds that's perfect for touring.

it suggests, that while having BRS installed allows for greater MAUW (472.5) it only comes on the expense of increased empty weight - 265.5 goes up to 288, which means effective payload stays the same..

looking at same specs it suggests that full tank economical speed endurance should be just short of 4 hours, meaning it burns just around 17l per hour (13kg).. now having two chaps and a bit of cargo as in my original post, would allow for just shy of two hours flight time.

Now I know with this kind of question I'm not going to make any friends, feel free to PM me, but allow me to be blunt - do microlight flyers bend the rules in their favor regarding MTOW? It looks like the machines are perfectly capable of lifting two decent men with full tanks, as the ikarus is now certified for tugging gliders and what not, but the number on the paper is there and it's tiny... do people respect that or does some +10kg /turning a blind eye generally happen?

It's a perfectly good question but the rules are the rules so they must be respected. There's no question that they aircraft are perfectly capable of flying overweight (many of the same types are also available as LSA aircraft at higher weights) but flying overweight is likely to cause all sorts of issues, not least insurance in the event of an accident. I would say the vast majority of pilots respect the MTOW but of course there may be some that don't but certainly no more than any other discipline of flying. 2 Hours endurance will get you most places in Ireland at C42 speeds.

Regarding touring, I generally fly with a group of other pilots and if there's any spare seats we'll distribute the weight accordingly (pax and baggage). A few years ago a few of us flew over to the LAA Rally at Sywell and we had friends also going by road so they took all of our stuff.

If you're looking to tour, a microlight is probably not the best machine for the job but if you're looking for low cost flying, a great selection of destinations and a community of great friends microlighting is the way to go. Come down to the Limetree fly-in on June 1st (bank holiday Monday) and see for yourself!)